Are there other theoretical methods that can be used to calculate electronic transport properties?
Transport of electrons in the presence of electric field and magnetic field can be described uisng Boltzmann transport equation. There are Classical and semi-classical formalisms and a detailed analysis can be found here.
I believe the plane-wave codes can utilise a form of the wave-function matching technique to calculate device modes coupled to scattering states in the bulk parts, see e.g. http://dx.doi.org/10.1103/PhysRevB.74.245404.